Transportation costs associated with an aqueous diluent portion of a formulated aqueous product can be a significant part of the cost of aqueous liquid products as used at a use locus. Products, such as sanitizing or cleaning solutions, when used in large amounts can be expensive to use due to transportation costs associated with the aqueous portion. For this reason, many commodity liquid products are shipped from the manufacturers as an aqueous concentrate, an aqueous alcoholic concentrate or as a viscous concentrate to be diluted in a dispenser with an aqueous diluent at the use locus or site. For example, liquid detergents and cleaning solutions used in hospitality locations, institutional or industrial installations such as hotels, hospitals, restaurants, and the like are often shipped as liquid concentrates that are mixed and diluted using a dispensing device at an appropriate ratio to obtain a useful solution.
The dilution of concentrates can be done in many ways, varying from, on one hand, simply manually measuring and mixing to utilizing a computer-controlled dilution device. One common dilution mode involves utilizing a dispensing device that combines, under mixing conditions, a flow of concentrate and a flow of diluent. The flow of the liquid diluent can be directed through an aspirator such that, as the diluent passes through the aspirator, a negative pressure arises inside the aspirator drawing the liquid concentrate into the aspirator to mix with the liquid diluent. Both Copeland et al., U.S. Pat. No. 5,033,649 and Freese, U.S. Pat. No. 4,817,825 disclose dispensers having aspirators for diluting liquid concentrates to produce liquid products in this general way. Such aspirator-type dispensers have been used for diluting a liquid concentrate of any arbitrary viscosity with a low viscosity liquid diluent to produce a use solution of intermediate or low viscosity, i.e. the viscosity of the product falls arbitrarily between the viscosity of the concentrate and the diluent.
A use solution of high viscosity is often desirable. Increased viscosity can increase clinging ability to surfaces of an inclined or vertical substrate for more effective and prolonged contact. Examples of applications where cling is important includes manual dishwashing detergents, hand cleaners, sanitizing toilet bowl cleaners, delimers, oven/grill cleaners and degreasers, etc. Some of such relatively viscous use solution can be made by diluting a low viscosity liquid concentrate with a low viscosity liquid diluent to form a very high viscosity dilute product.
Conventional aspirator systems are designed for a decrease in viscosity upon mixing a diluent and a concentrate and at best operate intermittently when provided with a high viscosity (50-2500 cP) concentrate. Such a conventional dispenser can also fail to accommodate a viscosity increase upon dilution to a use solution product with a viscosity of about 200-4000 cP. The typical dispenser has a standard aspirator with a venturi nozzle outlet and a throat opening to a downstream passageway for mixing the blended liquid derived from the aspirator nozzle and source of concentrate. Such a dispenser has venturi in close proximity to the throat, typically 3 mm or less, and has a diameter ratio of the diameter of the nozzle outlet to the diameter of the opening of the downstream passageway that generally falls between 1:1 and 1:1.4. This size ratio is adapted to dispensing low to medium viscosity concentrates in a diluent stream to form a use solution having a viscosity less than the typical liquid concentrate. Generally, the distance between the nozzle outlet and the throat in the prior art dispenser is about 2 mm or less. In a high viscosity product dispenser, made from a lower viscosity concentrate, failure can occur when the concentrate mixes with the diluent. The viscosity of the concentrate and the increase in viscosity can prevent flow through the dispenser that obtains proper aspirator action. Alternately the high viscosity of the concentrate or the use solution can prevent the correct operation of the aspirator. In this failure mode the diluent can pass through the dispenser with little or no concentrate pickup or mixing. A substantial viscosity increase can result in poor mixing, an intermittent flow or a blockage of flow through the dispenser. Further, even if the flow of use solution does not stop completely, the use solution may not be produced (or dispensed) over time at a consistent dilution or flow rate.
A substantial need exists to provide a dispenser that can dispense and dilute a concentrate in a dilute solution that exhibits a viscosity greater than the concentrate. The preferred dispenser of this invention will create a use solution of high viscosity, will consistently mix diluent and concentrate, will provide a controllable dilution ratio and will provide a consistent flow of use product. The first embodiments of this invention solve these problems by using a diluting dispenser or apparatus having a novel internal sizing adapted to the viscosity changes that occur during the dilution resulting in the consistent and accurate production of a use solution of higher viscosity than either the liquid concentrate or the liquid diluent.
The typical approach to prevent leaking from an aspirator is to shut off the water flow before the aspirator and allow residual diluent to drain out. However, with the large internal volume needed with the first embodiments of the present invention to have the required high efficiency aspirator when dispensing products that thicken when diluted, this some times is not an acceptable solution. The diluent will continue to drip for a period of from one to two minutes after the water valve has been shut off. The second embodiments of the present invention provide for relocating the shut off to the exit port of the aspirator and having a slide bar linkage actuate the water valve at the same time and thereby reduce or eliminate any leakage.